The Twitter cofounder is training for his first half-marathon later this year.

How long have you been running?Our friends went to New York for the summer and wanted someone in their house, so we moved in. Marin was so beautiful, and I'd run a bit before but thought, Oh, I should run here. So, my first run was our first weekend there.

I thought, I'm going to go run, you know, burn some calories, and I'd heard about Nike Plus, so I got it and went out. After my first run with it, I was like, "Oh, that's all I ran? Two miles?" It didn't look very impressive on the chart, but at least it was logged. Made me feel like I did something. The next day, I was like, "I gotta do more than that." You should see the chart now, it just goes up, up, up, then really up. I've gotten totally into it. Now, I'm obsessed with doing better each time. I'm just having fun trying to get to the 10-mile mark, then the 12.

That's a big jump in three months.It seems big, but because I see this chart, because I can visualize the progress, I just go. I can see the chart in my head when I run and I need the bar to be higher than the last time. It's the power of personal metrics. It's very gamelike, you know.

Do you run solo?Yes. The reason I really started running was for meditative purposes. I would pick some problem to have in my head while running. Not for the purpose of solving it, but for the purpose of having it bounce around in there. Like when you say you're going to sleep on it; I'm going to run on it. Then at some point later on, a solution falls out.

What are some issues or problems you have mulled over?Just a lot of Twitter stuff. One thing that's on our mind these days is growing the company. Not the technology so much, although that's a big part of the company obviously, but the culture. For example, we're a two-year old company and we have this bright spotlight on us and one of my concerns is that we end up like one of those child actors who found success early but then grew up all weird. I want to be more like Ron Howard, who was a child actor and now a really successful director. So how do you make sure you don't buy into the "Wow, if everyone is talking about us we must be great, we must be geniuses"? We're not. The key is to pay attention and to stay focused. Running helps me sort through all that.

Helps you not be so overwhelmed.Yes, yes, exactly, it seems like that's what it's like for a lot of people. Even though running is physically straining, it's mentally refreshing. Especially when you feel like you've accomplished something. That's the other thing about measurement: Wow! That was my longest run. You feel like celebrating, so it's exciting. Then you get into it more, you know. You start reading about, thinking, I should probably be drinking or eating differently. There's a few people who run here, and they say, "What did you do to do the 12-mile this weekend?" and I say I don't know, I don't know how it happened. I woke up and had a handful of cashews and went for a 12-mile run. And I don't know why it worked.You tweeted that you went out to run 10-K but did 20. How'd that happen?I got lost, but happily lost. Then I realized I was getting close to 10 miles and was feeling good, and I thought, I should just keep going. I'll get my Nike Plus chart to go way up. But I told my wife I was only going to be gone a half hour, and so I'm wresting with the idea of continuing. Finally, I decided to go back. When I got home, my wife was like "Where were you? I was going to call the police?" And I said, "You can't call the police and say, 'My husband is 45 minutes late.' They're not going to listen."

Do you know your pace?I'm pretty slow, just under 10-minute miles, but I don't care. It's much more enjoyable for me if I'm not straining to go faster.

Have you set any running goals?Secretly I want to...well, I always set my Nike Plus for 10-K, but I always do more. It's a mental thing: It's just 10, don't worry about it. Some of us are running the Rock 'n' Roll San Jose Half Marathon. So, basically, I want to get to a marathon, but it's not officially stated.

Which one?Well, I'm from Boston, so the Boston Marathon would be awesome, but qualifying is a serious deal. I remember when I was a kid [in Wellesley, Massachusetts], I'd climb a tree in our yard to watch the marathon.

What drew you to running, rather than some other sport like cycling?I love the simplicity of it. You need a pair of sneakers. I thought about tennis. But the more I thought about the whole thing—lessons, equipment, going to the courts—I said screw it, I'm just going to go buy a pair of sneakers and go running. It's very simple, but there's also a lot of strategy and opportunity if you want to go deeper. It reminds me of Twitter. I guess I'm drawn to simplicity.

Your favorite place to run?It's back in Boston where I grew up. Lake Waban around Wellesley College. It's beautiful. At home [in Larkspur, California] I just cross the street and follow a bike path along Richardson Bay. I go toward Mt. Tamalpais and into downtown Larkspur and just start getting lost. Getting lost is key to getting more mileage in. The other key is to run 10-K away from your house. You have to get home eventually.

Trails or road?I have some friends who are trying to get me to run trails. Since I'm fairly new to the distance thing, I'm a little wary of hills and stuff, but that being said, I really enjoy the experience of running on trails. It feels like you're going faster—trees and pebbles rushing by me. But there's also something to seeing this lone pathway ahead of you, you know?You've been running for three months, how are you different?I've been losing weight, which is great. In a job where you're on a computer all day, and we cater lunch and we put snacks in the kitchen, well we all started gaining weight, even though we try to pick healthy stuff, but inevitably you find the cashews. I noticed just the other day that I have more leg strength. Running's also helping my back. I haven't noticed any aches in a while.

How has Twitter influenced your running?Everyone comes out of the woodwork since I've been twittering about running. It's like, "You run? Oh, I run too. Let's run together." All of a sudden you're entered into this world, meeting people, talking to them about running. Twittering about it was key for me, just putting it out there. And that's the thing that's been happening in communication over the last 10 years; it's what I like to call social alchemy. Say I tweet that I ran 10-K today. Critics will say, "Who cares? That's not something I need to know." But if it reaches another runner, like my friend who invites me to join his trail-running group, that seemingly invaluable piece of information becomes something valuable. Alchemy, information into gold.

You mention sftechruns on your tweet...Yeah, other tech companies. I run on both weekend days, and one or two nights after work in the city, but those are social. The sftechruns [@sftechruns] are on Tuesdays—I join them every few weeks or so—and we're thinking about starting a weekly Twitter run. I want to get more accustomed to the social running thing because I think it's really a good culture-building exercise. I remember reading that Bob Marley, or somebody famous, would run with coworkers, or his band. I like that idea. You really connect with people so much better when you get out of the office. A lot of people go out for drinks, but going for a run would be much healthier. Plus, you're sharing that experience of struggling a little, of getting up a hill, so it's a bonding thing.

When do you know you've had a great run?I know I had a great run when I feel like I wasn't even trying. Like there was some invisible hand pushing me. I also enjoy when you're just "aw" afterward. It hurts, but in a good way.

If you need motivation to get out the door, what do you do?So far, the motivation has been the running itself. I'm looking forward to it a lot. And the personal metrics. If I miss a workout, it's not going to show up on my chart.

I got a little bit more serious about running when I got lightweight running shorts. And Dri-Fit socks. And a wicking shirt. Plus this piece of a sleeve thing that's a big pocket— you can put your keys and stuff in there. That's my running outfit right now. I used to run in big, oversized sweatpants and a sweatshirt and everything was sort of twisting around.One thing that really bugs me is when there's a zipper or coins jiggling. I need to mute that.

Do you have any advice to runners on how they can best use Twitter?Just put it out there. Once you promise [on Twitter] that you're going to run this weekend, then people who follow you will say, "So how'd it go?" It's just enough pressure to get you going.

I got some advice from an athlete friend of mine a long time ago: "As long as you're moving forward, don't worry." That was good advice for me. It doesn't make me feel like I'm giving up when I slow down. I'm still doing it. I'm still in the game.You run at night?My ideal time is to be finishing up the run as the sun is setting; it's just a beautiful time. And ideally, I run near water. I run along Richardson Bay. There's something about running near a large body of water that feels like you're drawing some energy in from it. There's so much to look at, the marsh, birds. It's really cool.

Did you run in Mexico?[Biz had returned from a business trip the day before] No, but I ran at sunset along the French Riviera, in Cannes. There was a nice trail, a boulevard. Where I started, there was a big carousel, lots of kids playing. It was fun because I was running along the water, but I was also dodging folks. I ran and ran until I got to a private beach and went and touched the water and just kind of said "I'm in France!" Know what I mean? Then I went back to my hotel, which was cool because it was this fancy hotel and I'm dripping with sweat and sand.

I ran in Lisbon, too. Beautiful city. I brought my iPhone with me because I didn't want to get lost. It has a great GPS—hit a button and it tells you where you are. I just ran all over, got lost on these cobblestone streets. I was only out for an hour and half, but I stopped a lot to check my location on the phone.

Will you start using training programs?Yes, I think so. I'm feeling like running is something simple enough, flexible enough, and I do enough travel so...I can pretty much run anywhere. It's superflexible. That's what I like about it.

What's on your playlist?I just made a running mix. It's funny, I'm learning that it doesn't matter what the song is, it's the pace of it. There are a few songs on my list that I never would think I'd like, but they actually make me run better and faster. I would love it if Nike Plus would say, 'You run faster to these songs, buy more like that.' [Looking at his iPhone] Okay, The White Stripes, music from the movie Donny Darko, Red Hot Chili Peppers. I downloaded Moby's extended remix of the James Bond theme. More White Stripes. Slumdog Millionaire soundtrack. I got some Eagles in there, "Hotel California." I don't know how that got in there. I like it though. It comes on and it's totally rich.

Nike Plus does all these little things, like when you do your longest or fastest run, Lance Armstrong or Tiger Woods comes on and congratulates you on your iPod. So, you're thinking while you're running, I'm not going to get Tiger Woods unless I run really fast or long. There was one time when I thought the run was going badly, and I thought, Nike Plus isn't going to give me any love. Then suddenly I hear, "Hi, this is Tiger Woods and that was your fastest mile yet." And I'm like, Wow, that's cool! And I tell my wife, "Tiger Woods told me I had my fastest run!" She's like, "I don't know what you're talking about." And I'm like, "C'mon, pop the bubbly!"